There are a number of devices taught in the prior art for converting energy from the flow of a fluid (such as air or water) to electrical energy.
For example, U.S. Pat. No. 4,412,417 teaches a turbine arranged to be anchored on the surface of a body of water for converting xe2x80x9cwave energyxe2x80x9d to electrical energy. The device includes a shaft having a helical flight displaced therearound, The flight is not enclosed and the waves passing along the flight causes the shaft to rotate, thereby generating electrical power. U.S. Pat. No. 4,849,647 teaches a similar floating turbine that floats on and is exposed to a body of water.
U.S. Pat. No. 5,664,418 teaches a turbine arrangement including vanes for concentrating the wind.
One difficulty faced by devices such as these is that the flow intensity of the fluid, whether wind or wave, is highly variable and dependent upon weather conditions. That is, in conditions wherein there is little or no wind, the above-described device would not produce much power, whereas a strong wind could lead to conditions which would damage the device. As such, these devices are impractical, as the amount of electrical power generated at a given time is highly variable and unpredictable. This is not the case with underwater currents, which are generally more constant both in terms of intensity and direction, making underwater currents more suitable as potential sources for electrical power.
U.S. Pat. No. 4,219,303 teaches an underwater power plant which is includes electrical generators and machine rooms within the device. Clearly, a device such as this is simply too large for use in streams or rivers and is suitable only for use in ocean currents.
U.S. Pat. No. 4,025,220 teaches a turbine for use in water or air which includes a xe2x80x9cflexible fluid current collectorxe2x80x9d for increasing the flow of a fluid, the device being arranged for use in either air or water. It is of note that the collector described is composed of fabric.
Clearly, a device that is arranged for generating electrical power from underwater currents that can also be used in streams and rivers and the like is needed.
According to the invention, there is provided a water driven turbine for converting the energy of an underwater current comprising: a hollow tubular open ended housing, said housing having an entry end for accepting the water and an exit end for releasing the water; a shaft mounted within the housing, said shaft arranged to rotate within the housing about an axis of rotation; connection means on the shaft for operably linking the shaft to a generator such that rotation of the shaft generates electrical power; blade means arranged about the shaft, said blade means extending along a length of the shaft; and a funnel mounted onto the entry end of the housing, said funnel having a mouth and a discharge, said mouth having a diameter greater than the diameter of the housing, said discharge having a diameter approximately equal to the diameter of the housing, wherein the discharge of the funnel is mounted onto the entry end of the housing such that the water entering the funnel at the mouth passes through the housing and contacts the blade means, thereby rotating the shaft and generating electrical power.
The generator may be positioned behind the exit end of the housing relative to the mouth of the funnel.
The diameter of the mouth may be approximately 50% greater than the diameter of the discharge.
The water driven turbine may include fins mounted on an upper surface and a lower surface of the housing for preventing twisting of the water driven turbine.
The fins may be mounted on the housing proximal to the exit end of the housing.
The water driven turbine may include buoyancy means mounted on the water driven turbine.
The buoyancy means may be mounted within the fins.
There may be three blade means or two blade means.
The water driven turbine may include tether means mounted within the funnel for stabilizing the water driven turbine.
One embodiment of the invention will now be described in conjunction with the accompanying drawings in which: